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Friday, 7 August 2009

Lime Water

London publicists for the Chartered Company described 'the flame' of the new gas which Mr. Winsor was advertising in 1808 as 'entirely free from smell'.However, they had to admit the audience had noticed 'a disagreeable odour in Mr. W.'s old lecture room'. Winsor washed the gas which he made by bubbling it through a solution of lime.

Chemists of the time knew that lime could be used in this way as a test for 'fixed air'.Accum had suggested the method in 1803 as a way of removing carbon dioxide from gas which had been made from distilled wood. William Henry also pointed out that 'sulphuretted hydrogen' was the cause of the 'offensive smell' from coal gas which 'resembled bilge water or the washings of a gun barrel'. He described the way to remove it using lime. Lime was used as the earliest means of cleaning up the smell from coal gas.

One of Winsor's assistants - a group of people he referred to as 'bungling smiths and low tinkers', was to claim the invention of lime purification for himself. This was Stephen Hutchinson who, during the 1830s, said that an astonishing range of gas making equipment was actually invented by him. He said that in this instance slaked lime was used 'accidentally' during some experiments which he carried out for Winsor at the Rhedarium in Green Street. This was a big demonstration of gas making with many important people present. As a result of the lack of smell, Hutchinson claimed, seven people present subscribed a fund of 70 guineas to start the company. How this accident is supposed to have happened was not explained. Hutchinson's inventions were all verified by letters from another reader, 'Clovis'. In a subsequent issue of Mechanics Magazine, 'Clovis' was unmasked as Mr. Joseph Hutchinson, oil gas works manager and Stephen's father.

The bad smell of gas very quickly became a problem for the new Chartered Company. As early as 1812 the Committee for Chemistry raised the subject with Frederick Accum. He advised them to use lime water. Samuel Clegg had already used this method this in the gas making plant he had set up 1811 to light Stoneyhurst College. At Stoneyhurst Clegg had 'used the scientific facilities at the College to experiment' with different purification methods. He had then devised a 'lime machine' that allowed the newly made gas to be passed 'through lime water'. Clegg's next private installation was in London, at Ackerman's Strand bookshop. There he met with what was to become a major problem with 'wet lime' purification - complaints about the waste effluent from his lime machine, which had been allowed to run into the public drains.

Once in London, and in the employment of the Chartered Company, Clegg continued to add mechanical refinements to his lime purification system. He began to use a semi solid process in which the gas bubbled up through the lime itself. So that residues would not build up and clog the mechanism he included 'a shaft ... furnished with teeth' to scrape out the openings. In 1818, John Malam, one of Clegg's 'young men', improved the design of this equipment. For the next twenty-five years Malam and Clegg's system remained as standard practice for purification in most gas works. The gas might have been cleaner but disposal of the smelly waste water remained a big problem.